Abstract PD6-1: Tumor spheres growing from peripherally circulating tumor cells exhibit stem cell features

Abstract Background: Among the cells that are disseminated from a malignant tumor only very few are capable to resettle in distant organs and grow into life-threatening metastases. Therefore, the question arises how and whether such cells which have the potential to grow into metastases can be detected. It has been shown that a subpopulation of cells from breast cancer tissue can form so-called mammospheres with stem cell features. Here we show that such tumor spheres can also be grown from peripherally circulating tumor cells from breast cancer patients in different stages of disease Materials and Methods: Using a nondissipative approach with only one enrichment step of red blood cell lysis, the cells from the pellet, containing the white blood cells together with the putative tumor cells were cultured under conditions favoring the growth of epithelial cells. At 7, 14 and 21days the cell cultures were inspected for the appearance of spheroids staining with anti-EpCAM, anti-CD24 and anti-CD44 antibody and.expressing ALDH1. Results: Peripherally circulating cells from patients with malignant tumors in different stages of disease were analyzed for the presence of circulating epithelial tumor suspect cells and the frequencies of tumorspheres. Tumorspheres could so far be grown from 79% of 36 patients in whom more than 1700/ml epithelial tumor suspect cells were detected. Numbers of tumorspheres varied from 1 to 29 /ml and correlated with the aggressiveness of the tumor. Surprsingly the numbers were highest in patients after surgery who had not yet received any systemic therapy. The size of the spheres increased from day 7 to day 21. The spheres were negative for CD24 and positive for CD44. They highly express ALDH1 and thus exhibite typical features of stem cells. Conclusion: Here, we demonstrate that the circulating tumor cells, detected in our approach contain a subpopulation with stem cell-like properties capable of growing into tumorspheres. The frequency and growth potential of cells capable of forming spheres seems to be dependent from the properties of the primary tumor. The possibility to grow tumorspheres from peripherally circulating tumor cells may open up a new field, where the relevant cells with stem cell properties from individual patients can now be specifically analysed further for genetic endowment, transcriptional activity, heterogeneity and stem cell markers. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr PD6-1.